May witnessed an all-time low for virus-laden emails and a record high for spam, according to figures released by security services firm BlackSpider Technologies. 

The number of emails containing a malicious program made up fewer than one per cent of all emails seen by BlackSpider, while junk emails represented 87.74 per cent.
The company said that the record-breaking spam figure was boosted by a spike in traffic between 21 and 23 May, when UK businesses were flooded with more than 250 million advertising emails.

The surge came from a botnet made up of more than 150,000 compromised PCs and peaked on 22 May. 

James Kay, chief technology officer at BlackSpider, pointed to the spam attacks on Blue Security as a warning not to be complacent. "Spam is still a potent threat despite it being relatively old news," he said.

"First we saw what happened to Blue Security, then just a week later we saw a spam spike which could be crippling for anti-spam service providers and anti-spam products."

Kay said that, even though the number of emails carrying viruses was just 0.73 per cent, the number of compromised machines used as spambots showed that virus infection is still a widespread problem.

Netsky.P continued to top the malware chart, followed by Trojan-Spy.HTML.Bankfraud.od in second place and Download.Trojan in third place.